1. Field of the Invention
The present invention relates generally to methods and apparatus for combining parenteral solutions and other liquids. More particularly, the present invention relates to methods for transferring a donor liquid into a recipient container filled with a recipient liquid where excess liquid in the recipient container is exhausted from the recipient container and captured.
Commonly-owned copending application US 2009/0292271, the full disclosure of which is incorporated herein by reference, describes a “dosing pen” device capable of combining liquid buffers and anesthetics. The dosing pen includes a fluid transfer device which utilizes a transfer needle 36 (the reference numbers in this paragraph refer to the '271 publication) and an exhaust needle 38 positioned in a knob 12 which can removably receive an anesthetic cartridge 28 so that distal ends of both the transfer needle and exhaust needle penetrate a septum on the anesthetic cartridge. A buffer cartridge 16 positioned within a housing 14 is also attached to the knob 12 so that a proximal end 50 of the transfer needle 36 can penetrate a septum 15 of the buffer cartridge when the knob is fully advanced onto the housing. A pusher 20 is provided to drive a plunger 58 on the buffer cartridge to transfer buffer through transfer needle 36 into the anesthetic cartridge 28 and to simultaneously exhaust anesthetic from the anesthetic cartridge back into a reservoir 72 in the housing 14 through the exhaust needle 38. While the dosing pen of the '271 application is advantageous in many respects, the excess buffer, which is exhausted through exhaust needle 38, ends up in the housing 14 and is subject to leakage.
An improved dosing pen is described in commonly owned US2011/0166543, the full disclosure of which is incorporated herein by reference. As illustrated in FIG. 1 herein, the '543 publication shows a dosing assembly 10 which connects a buffer cartridge 12 and an anesthetic cartridge 14 with a transfer needle 16 entering through septum 18 and septum 20, respectively. An exhaust needle penetrates septum 20 of the anesthetic cartridge and allows excess anesthetic to vent into a collection reservoir 26 in a housing 24 which hold the needles. The chamber is “sealed” and intended to be contain the excess liquid 28 to prevent leakage. While certainly an improvement, the chamber will usually need at least a small vent to permit the displacement of air initially present in the chamber and remains subject to leakage as the dosing pen is manipulated and reoriented, particularly when a new anesthetic cartridge is being exchanged for a buffered anesthetic cartridge. Even if leakage through the vent were inhibited, for example using a gas permeable liquid barrier over the vent, there is still a risk that pooled liquid within the chamber could submerge the outlet end of the exhaust needle, resulting in backflow of the excess fluid.
For these reasons, it would be desirable to provide improved methods and apparatus for transferring and combining liquids, such as buffer solutions and anesthetics, where the liquids are held in conventional containers with needle-penetrable septums and dispensing plungers. In particular, it would be desirable to provide systems and methods which allow for transfer of a donor liquid, such as a buffer solution, into a recipient solution, such as an anesthetic, which fills a recipient container where the displaced recipient solution can be vented or exhausted into a reservoir with a minimum risk of backflow or leakage from the reservoir. At least some of these objectives will be met by the inventions described hereinbelow.
2. Description of the Background Art
US 2011/0166543 and US2009/0292271 have been described above. Glass vials and cartridges for storing medical solutions are described in U.S. Pat. Nos. 1,757,809; 2,484,657; 4,259,956; 5,062,832; 5,137,528; 5,149,320; 5,226,901; 5,330,426; and 6,022,337. Injection pens which employ drug cartridges are described in U.S. Pat. No. 5,984,906. A particular disposable drug cartridge that can find use in the present invention is described in U.S. Pat. No. 5,603,695. A device for delivering a buffering agent into an anesthetic cartridge using a transfer needle is described in U.S. Pat. No. 5,603,695. Other patents and applications of interest include U.S. Pat. Nos. 2,604,095; 3,993,791; 4,154,820; 4,630,727; 4,654,204; 4,756,838; 4,959,175; 5,296,242; 5,383,324; 5,603,695; 5,609,838; 5,779,357; and U.S. Patent Publ. No. 2004/0175437